1. Field of the Invention
The present invention relates to a system for controlling a multiple speed axle in an automated mechanical transmission system. More particularly, the invention relates to a system for controlling, either manually or automatically, a multiple speed axle that is attached to a medium duty automated transmission, to insure proper and safe shifting between axle speeds.
2. Description of the Prior Art
It is well known in the prior art to provide both automatic and manual transmission systems with multiple speed axles for high and low range speed modes. For example, when a vehicle operator requires more torque to improve climbing power of the vehicle for off-road driving, it is desirable to utilize a low speed mode. Conversely, when the vehicle is in operation on a traditional well-maintained roads, a high speed mode is used.
In one known multiple speed axle application for a manual transmission, the vehicle operator is responsible for properly and simultaneously operating the vehicle, the axle, the transmission and the engine. Thus, the operator must simultaneously ensure that the vehicle speed stays within a proper range of speeds to facilitate safe shifting, maintain the present transmission gear ratio and manipulate the engine throttle to effect a synchronous condition in the axle, in order to properly complete an axle range shift. Once the operator determines that the axle range shift has been completed, the driver may proceed with normal driving and transmission shifting procedures. To avoid much of this complexity and also to protect the axle, transmission, engine and the vehicle; many drivers only perform these axle range shifts when the vehicle is stopped.
The prior art also discloses multiple speed axles in automatic and semi-automatic shift implementation for mechanical transmissions. In these types of systems, the vehicle operator is required to know when the engine will prompt a transmission shift so as to avoid performing an axle shift during the transmission shift operation. Further, it is the operator's responsibility for determining the proper speed in which to accomplish a safe axle shift and to synchronize the vehicle drive shafts within the axle. As with manual transmission systems, once the operator determines that it is safe to proceed with an axle shift, the operator manually causes a torque interruption and synchronizes the multiple speed axle for engagement. Ultimately, safe shifting of the multiple speed axle is wholly dependent upon the operator knowing when not to cause a transmission shift.
Known prior art axle shift control systems are undesirable as they require that the vehicle operator have a relatively high level of skill and experience to properly operate the vehicle and to know when an axle shift can be safely accomplished. For example, known axle shift systems places the burden on the operator to inhibit transmission shifts, break torque and safely engage the split axle to permit the engine to achieve the desired gear ratio. Accordingly, there is no current system available that indicates to the driver when an axle shift may be safely accomplished or that automatically controls an axle shift operation.